1. Field of the Invention
The present invention relates to an ink jet recorder, and more particularly to an improvement in an ink supply system.
2. Description of the Prior Art
Ink jet recorders are known to have a print mode in which ink is discharged from a head onto a record paper to print characters and a supply mode in which, when the ink in an ink supply tnak used as an ink supply source to the head is depleted, ink is supplied to the ink supply tank from an ink replenishment tank which is separately arranged from the ink supply tank, (Japanese patent publication No. 61934/1980).
Ink jet recorders are also known to have an ink supply path extending from an ink supply tank to a head and returning to the ink supply tank, with switching means and a pump arranged in the supply path so that a recirculation mode for recirculating the ink in the supply path can be established, in addition to the print mode, by controlling the switching means and the pump in order to eliminate air bubbles and clogging in the supply path, (Japanese patent publication No. 159227/1980).
However, in each of those prior art ink jet recorders, only one mode, in addition to the print mode, can be established.
An ink supply system of the ink jet recorder needs joints in a feed pipe for supplying the ink from the supply source to the head and an return pipe for the ink from the head. Those joints are frequently disassembled for maintenance purpose but the disassembling and assembling of the joints are not easy. It is necessary to prevent the ink from flowing out of the pipe when the joint is disassembled. This is an even more serious problem in an ink jet recorder having a plurality of heads arranged.
On the other hand, in a prior art ink jet recorder, the print head, the ink supply tank for the head and the valve and the pump for circulating the ink to remove the air bubbles or clogging are connected through the ink supply tube. Accordingly, those elements form a unitary ink supply system and individual elements cannot be removed individually.
In an ink jet recorder having a plurality of heads to increase a print efficiency, it is necessary to arrange a number of long supply tubes. Thus, the ink supply paths are more complicated. This causes the assembly and disassembly of the elements to be more difficult and raises potential problems of misconnection of the tubes, evaporation of ink and introduction of air into the ink supply paths.